It is thought the bombardment is a bid to crush Hamas’ military capability before Israel deploys ground forces.

Israel’s cabinet, headed by president Benjamin Netanyahu, mobilized up to 75,000 reservists with 16,000 already called to active duty.

The Arab world is rallying round the Palestinian territory, prompting fears the conflict could spread.

Tunisia’s Foreign Minister Rafik Abdessalem denounced the attacks when visiting the Gaza Strip yesterday. In Cairo, Egypt’s president Mohamed Morsi held four-way talks on the crisis with the Qatari emir, the prime minister of Turkey and Hamas leader Khaled Meshaal.

Mr Abdessalem said: “Israel should understand that many things have changed and that lots of water has run in the Arab river.

“Israel should realise it no longer has a free hand. It does not have total immunity and is not above international law.

“What Israel is doing is not legitimate and is not acceptable at all.”

Israel began its campaign against Gaza on Wednesday with the assassination of Hamas’ military chief, Ahmed Jabari.

This was followed by an air bombardment designed to stop Hamas firing rockets at southern Israel. Palestinian militants have responded by firing 500 rockets over the past three days.

The conflict escalated on Friday when Hamas targeted Jerusalem and Tel Aviv – the centres of Israeli government and commerce.

The latest round of Israeli air strikes destroyed the office of Hamas Prime Minister Ismail Haniyeh and the Hamas Interior Ministry. Hamas retaliated yesterday by targeting the Israeli city of Ashod and firing a rocket at Tel Aviv. It was shot down by Israel’s Iron Dome rocket-defence system.

In all, 40 Palestinians, including 13 civilians, and three Israeli civilians have been killed since the Israeli operation began.

Among those caught in the conflict were terrified Brits living in Israel.

Leeds-born Daniel Lazimi, 25, said: “Hamas is coming for us in Jerusalem. The sirens went off this morning and we all had to lie on the ground for 15 minutes and hope the place didn’t go up in smoke.

“We’re good people and a good nation who want peace.”

International leaders were working hard to diffuse the conflict last night.

In a call to Netanyahu, US President Barack Obama discussed options for “de-escalating” the situation.

Prime Minister David Cameron and Foreign Secretary William Hague have urged both Israel and the Palestinians to make efforts to halt the violence.

But they made clear they thought Hamas bears the greatest responsibility for the current crisis, as well as the ability to bring it most swiftly to an end.